Securing and Maintaining an Exchange Server 2003 Implementation

One of the greatest advantages of Exchange Server 2003 is its emphasis on security. Along with Windows Server 2003, Exchange Server 2003 was developed during and after Microsoft's Trustworthy Computing initiative, which effectively put a greater emphasis on security over new features in the products. In Exchange Server 2003, this means that the OS and the application were designed with services "Secure by Default."

With Secure by Default, all nonessential functionality in Exchange must be turned on if needed. This is a complete change from the previous Microsoft model, which had all services, add-ons, and options turned on and running at all times, presenting much larger security vulnerabilities than was necessary. Designing security effectively becomes much easier in Exchange Server 2003, because it now becomes necessary only to identify components to turn on, as opposed to identifying everything that needs to be turned off.

Patching the Operating System Using Software Update Services

Although Windows Server 2003 presents a much smaller target for hackers, viruses, and exploits by virtue of the Secure by Default concept, it is still important to keep the OS up to date against critical security patches and updates. Currently, two approaches can be used to automate the installation of server patches. The first method involves configuring the Windows Server 2003 Automatic Updates client to download patches from Microsoft and install them on a schedule. The second option is to set up an internal server to coordinate patch distribution and management. The solution that Microsoft supplies for this functionality is known as Software Update Services (SUS).

SUS enables a centralized server to hold copies of OS patches for distribution to clients on a preset schedule. SUS can be used to automate the distribution of patches to Exchange Server 2003 servers, so that the OS components will remain secure between service packs . Software Update Services may not be necessary in smaller environments, but can be considered in medium- sized to large organizations that want greater control over their patch management strategy.

Using Front-End Server Functionality

The OWA component of Exchange Server 2003 can be further secured and optimized through the use of a dedicated Exchange Server 2003 front-end server. A front-end server is an Exchange server that acts as a proxy for mail access. No working databases are kept on a front-end server; the front-end server relays requests from clients to the back-end Exchange mailbox server.

In Figure 4.7, the front-end server SFEX01 is set up in the DMZ of CompanyABC's firewall. Secure Sockets Layer (SSL) encryption is used by clients to access the front-end server. The front-end server then relays client requests from the Internet to the back-end SFEX02 server. This configuration helps secure the back-end server and also offloads the data decryption responsibilities from the back-end mailbox servers. For more information on front-end/back-end design, see Chapter 10, "Outlook Web Access 2003."

Figure 4.7. Front-end/back-end Exchange server configuration.

Implementing Maintenance Schedules

Exchange uses the Microsoft JET Database structure, which is effectively the same database engine that has been used with Exchange from the beginning. This type of database is useful for storing the type of unstructured data that email normally carries, and has proven to be a good fit for Exchange Server. Along with this type of database, however, comes the responsibility to run regular, scheduled maintenance on the Exchange databases on a regular basis.

Although online maintenance is performed every night, it is recommended that Exchange databases be brought offline on a quarterly or, at least, semiannual basis for offline maintenance. Exchange database maintenance utilities, eseutil and isinteg , should be used to compact and defragment the databases, which can then be mounted again in the environment.

Exchange databases that do not have this type of maintenance performed run the risk of becoming corrupt in the long term , and will also never be able to be reduced in size . Consequently, it is important to include database maintenance into a design plan to ensure data integrity.

Using Antivirus and Backup Solutions

It has become a must for organizations to employ antivirus and backup solutions for Enterprise email applications. As previously mentioned, one of the major advantages of Exchange is that the OS and the application itself support advanced backup and antivirus technologies that can be tied into by third-party software resellers . This third-party support is broad, and should be part of any Exchange design.